In the aforementioned parent application Ser. No. 648,170, a process is disclosed for upgrading lignitic-type coals including brown coal, lignite and subbituminous coals, to render them more suitable as a solid fuel as a result of the thermal restructuring thereof, producing an upgraded carbonaceous product which is stable, resistant to weathering and of increased heating value, approaching that of bituminous coal. As a result of such process, the vast domestic deposits of lignitic-type coal are converted into a useful fuel and provide a potential solution to the present energy crisis.
In addition to the large domestic deposits of lignitic-type coals, vast quantities of cellulosic type materials, both naturally occurring, such as peat, as well as waste materials derived from lumbering operations and agricultural wastes, are generated each year, which are available in a form unsuitable for efficient use as a commercial fuel. Such waste cellulosic materials such as sawdust, bark, wood scrap, branches and chips from lumbering operations, as well as various agricultural waste materials such as cotton plant stalks and the like, have heretofore represented a waste disposal problem. There has, accordingly, been a long felt need for a process for converting such cellulosic materials into valuable fuel products, thereby not only providing a potential solution to the fuel shortage and present energy crisis, but also eliminating the expense in disposing of such waste materials.
In addition to the foregoing problems, Federal and state regulations, such as enacted by the Environmental Protection Agency, as well as by the state of California, have imposed relatively stringent limitations on the quantity of sulfur in heating oils that can be burned by public utilities for generation of electricity and steam power. Current EPA regulations permit a maximum sulfur content per pound of heating oil of about 0.7%, whereas the state of California has imposed regulations limiting the sulfur content to a maximum level of 0.3% sulfur in certain areas. In order to comply with these regulations, it has heretofore been necessary to blend off domestic heating oils of relatively high sulfur content with low-sulfur heating oils imported from overseas in order to provide a residual blend having a sulfur content within the permissible limits. The premium cost of such foreign low-sulfur heating fuels makes this practice not only costly, but also increases our reliance on foreign oil sources. The foregoing problem is overcome in accordance with the present invention by providing an extremely low sulfur and low ash coke-like product which upon comminution can be admixed with high sulfur heating oils, providing a residual liquid slurry blend which meets regulatory requirements with respect to sulfur content.